The long-standing, generally recognized need for a better way to provide insulation for conductors such as the series loops of the stators of large, fluid-cooled, electric generators was finally met by the invention of the above-referenced patent application. Thus the difficulty and high labor cost of the standard manual taping and patching procedure of the prior art can be avoided and the shortcomings and derelictions of the potting and casting attempts of the prior art can be overcome by applying the principles of that invention. In essence, according to those principles a composite body of insulating material is formed over the exposed part of a series loop by enclosing that part in a clamshell mold of thermoplastic resin insulating material, then filling the mold with thermosetting resin insulating material and curing the latter and thereby bonding it to both the shell and the exposed part of the series loop. By virtue of the fact that two half shells of the clamshell mold are formed for adjustable interfitting engagement of their overlapped opposed edge portions the mold can be easily assembled and secured in place around the part of a series loop to be insulated. Then the thermosetting resin material can be injected into the mold and cured at room temperature to bond the resulting integral composite body of mold and fill to the exposed part of the conductor to be insulated. The thermosetting resin material thus on curing bonds well to both the thermoplastic mold and to the metallic conductor and in addition to having requisite dielectric strength has good shelf life, flowability enabling complete filling of the mold under moderate pressure, and in cured form is resistant to cracking on accelerated thermal cycling tests.